Quality of service based arbitrations optimized for enterprise solid state drives

ABSTRACT

A method and apparatus for operating a solid state drive is disclosed comprising receiving at least two commands from a host requiring an action by the solid state drive in a preliminary order, ordering the at least two commands based upon a quality of service classification for the at least two commands to a final order and executing the at least two commands on the solid state drive in the final order, wherein an operational parameter of the solid state drive is modified by at least one of the at least two commands.

FIELD OF THE DISCLOSURE

Aspects of the disclosure relate to memory arrangements. Morespecifically, aspects relate to solid state drives (SSDs) that areoptimized for enterprise operations based on quality of service basedarbitrations.

BACKGROUND OF THE DISCLOSURE Field of the Disclosure

NVM Express (NVMe) is a standard that has been created to allownon-volatile storage media to be accessed when the media is attached toa PCI Express (PCIe) bus. NVMe may be used with a variety of types ofnon-volatile storage media. One such type of media is a SSD. The NVMestandard was created to focus on several features, includinginput/output (I/O) operations between a host device and a memory device.The NVMe standard allows for different manufacturers of SSDs, forexample, to be used with a host computer, provided that the standard ismaintained.

NVMe uses different queues to achieve processing of data. As anon-limiting example, NVMe uses a paired submission queue and acompletion queue to accept data from a host and to notify a host thatprocessing is complete. As an example, host software, located within ahost computer, may place a command into the submission queue for an SSD.The SSD, non-volatile storage media, with an accompanying controller,may process the command on the submission queue and then placecompletions on an associated completion queue.

Quality of service is an important factor in the design of anon-volatile memory. Maintaining high levels of quality of service,despite high workloads, is important for the overall performance andquality of a user. Commands that are placed upon the submission queue,for example, should be processed in not only an orderly fashion, butalso within a predefined time limit so that latency is not experienced.Conventional non-volatile memory arrangements, however, receive commandsin a serial format and process these commands as received. Somecommands, which are not required to be immediately processed, may beimmediately processed, while other commands that require to be processedexpeditiously, may be forced to wait for processing. The processing,therefore, is non-optimal.

There is a need to perform processing of commands in an expeditiousmanner for non-volatile memory arrangements, such as solid state drives.

There is also a need to perform an arbitration between differentcommands in queues such that processing occurs on the commands that aremore urgent.

There is a further need to provide for increased quality of service forsolid state drives compared to conventional systems.

SUMMARY OF THE DISCLOSURE

The following summary is provided for describing aspects of thedisclosure and should not be considered limiting of the scope of theaspects described. A method and apparatus for operating a solid statedrive is disclosed comprising receiving at least two commands from ahost requiring an action by the solid state drive in a preliminaryorder, ordering the at least two commands based upon a quality ofservice classification for the at least two commands to a final orderand executing the at least two commands on the solid state drive in thefinal order, wherein an operational parameter of the solid state driveis modified by at least one of the at least two commands.

In one non-limiting embodiment, a method of operating a solid statedrive, is disclosed comprising receiving at least two commands from ahost requiring an action by the solid state drive in a preliminaryorder, ordering the at least two commands based upon a quality ofservice classification for the at least two commands to a final orderand executing the at least two commands on the solid state drive in thefinal order, wherein an operational parameter of the solid state driveis modified by at least one of the at least two commands.

In another non-limiting embodiment, a method of operating a memoryarrangement is disclosed comprising: receiving at least two commandsfrom a host through an interface of the memory arrangement, timestampingeach of the at least two commands upon receipt of the commands at theinterface, arbitrating each of the at least two commands to create afinal order for the performing each of the at least two commands andexecuting the at least two commands in the memory arrangement in thefinal order, wherein an operational parameter of the memory is modifiedby at least one of the at least two commands.

In another non-limiting embodiment, a device controller for a memoryarrangement device is disclosed comprising: an interface moduleconfigured to transmit and receive data from at least one memory arrayof the memory arrangement device, a host interface module configured totransmit and receive data from a host, a time stamp arrangementconfigured to record a time when a command is received from the hostthrough the host interface module, the time stamp arrangement connectedto the host interface module, a command arbitration arrangementconnected to the host interface module, the command arbitrationarrangement configured to receive commands received by the hostinterface module and arbitrate an operational order for the receivedcommands, a command queueing arrangement connected to the host interfaceand the interface module, wherein the command queueing arrangement isconfigured to accept commands placed in an order by the commandarbitration arrangement.

In another non-limiting embodiment, a memory device is disclosedcomprising: at least one memory array configured to store data providedto the array; an interface module configured to transmit and receivedata from at least one memory array, a host interface module configuredto transmit and receive data from a host, a time stamp arrangementconfigured to record a time when a command is received from the hostthrough the host interface module, the time stamp arrangement connectedto the host interface module, a command arbitration arrangementconnected to the host interface module, the command arbitrationarrangement configured to receive commands received by the hostinterface module and arbitrate an operational order for the receivedcommands and a command queueing arrangement connected to the hostinterface and the interface module, wherein the command queueingarrangement is configured to accept commands placed in an order by thecommand arbitration arrangement.

In another non-limiting embodiment, an arrangement for operating a solidstate drive is disclosed comprising means for receiving at least twocommands from a host requiring an action by the solid state drive in apreliminary order, means for ordering the at least two commands basedupon a quality of service classification for the at least two commandsto a final order and means for executing at least one command on thesolid state drive of the at least two commands in the final order,wherein an operational parameter of the solid state drive is modified byat least one of the at least two commands.

In another non-limiting embodiment, an apparatus for operating a memoryarrangement is disclosed comprising means for receiving at least twocommands from a host through an interface of the memory arrangement,means for timestamping each of the at least two commands upon receipt ofthe commands at the interface, means for arbitrating each of the atleast two commands to create a final order for the performing each ofthe at least two commands, wherein the means for arbitrating isperformed through a weighted round robin algorithm and means forexecuting the at least two commands in the memory arrangement in thefinal order, wherein an operational parameter of the memory is modifiedby at least one of the at least two commands.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above recited features of the presentdisclosure can be understood in detail, a more particular description ofthe disclosure, briefly summarized above, may be had by reference toembodiments, some of which are illustrated in the appended drawings. Itis to be noted, however, that the appended drawings illustrate onlytypical embodiments of this disclosure and are therefore not to beconsidered limiting of its scope, for the disclosure may admit to otherequally effective embodiments.

FIG. 1 is a non-volatile memory (NVMe) arbiter processing commandqueues.

FIG. 2 is a NVMe weighted round robin (WRR) arbiter processing commandsfor urgent, high priority, medium and low priority as well asadministrative commands.

FIG. 3 is a block diagram for a memory system.

FIG. 4 is a flow chart for a method of processing a command in onenon-limiting aspect described.

To facilitate understanding, identical reference numerals have beenused, where possible, to designate identical elements that are common tothe figures. It is contemplated that elements disclosed in oneembodiment may be beneficially utilized on other embodiments withoutspecific recitation.

DETAILED DESCRIPTION

Some embodiments will now be described with reference to the figures.Like elements in the various figures will be referenced with likenumbers for consistency. In the following description, numerous detailsare set forth to provide an understanding of various embodiments and/orfeatures. It will be understood, however, by those skilled in the artthat some embodiments may be practiced without many of these details andthat numerous variations or modifications from the described embodimentsare possible. As used herein, the terms “above” and “below”, “up” and“down”, “upper” and “lower”, “upwardly” and “downwardly”, and other liketerms indicating relative positions above or below a given point orelement are used in this description to more clearly describe certainembodiments.

Aspects of the present disclosure relate to computer operations andcomputer storage and specifically, enhancing operations of a storagedevice that is connected to a computer host. The function of the memoryarrangement is to accept data and store the data until needed again by auser or the host. The arrangement may be configured to accept bursts ofdata, depending on the computer process performed, therefore the datastorage arrangement is configured with multiple memory units thatprovide for various states of usage. Certain sections of the datastorage arrangement are configured of memory systems that provide forfast action (low latency) so that computer processes may be conducted ata rapid pace. Such low latency performance may be accomplished by singlelayer cell (SLC) memory configurations. If bulk amounts of data arerequired to be stored, multiple layer cell memory configurations mayalso be present, such as triple level cell (TLC) memory configurations.The data storage arrangement may have an interface that allows the datastorage arrangement to connect with the host computer. The interface maybe a SAS Interface or Serial ATA (SATA) compatible interface, as anon-limiting embodiments. The memory storage may have a configuration toallow for plug and play capability. Although described as having a SATAcompatible interface, the memory storage device may be provided with aconfiguration which allows for access by wireless technology. In onenon-limiting embodiment, 802.11ac technology may be used to provide forfast performance for smooth streaming. Wireless technology may use, forexample, between 2.5 GHz to 5 GHz frequencies for connection. In someembodiments, the storage may allow users to choose the frequencies forwireless connection. While being described as SATA compatible, othertypes of interfaces may be used.

Auxiliary connections may be provided to the data storage arrangement toallow for additional options for inputting data directly to the datastorage arrangement without interfacing with the host. Such direct inputof data may be provided through placement of an integrated securedigital card to offload or copy data. Other auxiliary connections may beprovided for additional input/output operations. Such connections may beUSB 2.0, USB 3.0, Firewire or other hard wired configurations. GigabitEthernet interfaces and connections may also be used.

The data storage arrangement may be configured with a separate powersupply or may be run through other power supply, such as from a computermother board. In some embodiments, an internal battery may be providedto power the data storage arrangement as an independent entity. Suchconfigurations may be provided such that the data storage arrangement isa portable unit. In such data storage arrangement configurations, thepower supply means may be sufficient to power a host and/or charge ahost, such as a mobile cellular phone, personal computer, tablet, cameraor other configuration. The data storage arrangement may also have abattery indicator to allow a user to understand the amount of charge inthe data storage arrangement from a visual inspection. Such batteryindicators may be, for example, low energy consumption light emittingdiode technology. In specific embodiments, the data storage arrangementmay be provided with a circuit to allow for charging and preventovercharging of the system if the data storage arrangement is connectedto an outside power supply for an extended period. In some embodiments,circuitry may be used to determine if a threshold of inactivity has beenreached for the storage system, thereby causing the system to enter alow power consumption mode, conserving battery power.

In one non-limiting embodiment, a controller is provided to controlactions of the data storage arrangement as required by the host. Thecontroller may also be configured to perform maintenance activities forthe data storage arrangement to allow for efficient use. The controller,for example, may be an application specific integrated circuit (ASIC) orother configuration that accepts commands from a host and then controlsoperations of the solid state drive or memory arrangement.

Internal software may be provided with the data storage arrangement toallow for efficient storage and read capability of data on the system.Such internal software may be used such that the data storagearrangement can be used as a portable media server to wirelessly streammedia to a host or output device. Such output devices may include, butnot be limited to, smart televisions, smart phones, stereo audio system.The internal software may also be provided such that the access of datamay be performed by cloud applications designed for interface with thedata storage arrangement.

The internal software of the data storage arrangement may also beconfigured to provide for security of the data storage arrangement.Safeguarding of material provided on the data storage arrangementprevents unauthorized access to sensitive information contained on thesystem. Security protocols may take several forms. Protocols may be inthe form of password protection, such as a Wi-Fi password protection. Inembodiments, software may be used in conjunction with the data storagearrangement to allow the data storage arrangement to create a hardwarelock. Such hardware locks, for example, may prevent access to a hostcomputer through a universal serial bus connection.

Memory arrangement software may also provide other benefits. Suchbenefits can include diagnostic support of the memory arrangement. Dataobtained may be directly supplied to a user or may be fed into othertypes of software that may analyze obtained data. In one exampleconfiguration, two different modes may be provided. A first mode mayprovide a quick test software program may be provided with thecapability to check the data storage arrangement for major performanceproblems. A second mode may provide a full test mode which may also beprovided to provide detailed status information to a user. Data may beprovided to the user which may include, for example, a firmware versionof the software, a total amount of memory of the data storagearrangement, the amount of memory storage used, storage divisionsprovided on the data storage arrangement, memory block errors, energyusage, age of the device and similar data.

The internal software may also be used as a server system wherein incertain embodiments, Digital Living Network Alliance (DLNA) enabledsoftware is incorporated. Such software allows for quick file transferand error checked operation as a server. In some embodiments, theinternal software may be provided with the capability to use filetransfer protocol (FTP) to enable the transfer of content to and fromthe memory storage in public access folders. The data storagearrangement may also provide for either a secured log in or an anonymouslogin capability.

In specific embodiments, the data storage arrangement may be configuredsuch that the system interacts with cloud storage systems or other datastorage systems. In the event that the data storage arrangementapproaches the limits of storage capability, the data storagearrangement may allow for some of the data to be stored on cloud basedsystems or other data storage systems. Selection of the data to bestored on such external storage systems may be governed by thecontroller which is configured to determine what sections of data may beappropriately stored in cloud based systems to minimize latency forusers. The storage system may have a unique identifier MAC address anddevice name to allow the system to operate on an independent basis. Thestorage system may also be operated in a configuration that allows forthe system to clone a MAC address of a computer that is attached.

The overall capacity of the data storage arrangement may vary accordingto the different embodiments provided. Capacities 1 TB, 2 TB up to 64 TBmay be provided, as non-limiting embodiments. Different form factors mayalso be provided. In the illustrated embodiment, a form factor of 2.5inches is provided. Other form factors such as 1.8 inch or 3.5 inch mayalso be used. Compatibility of the data storage arrangement may beprovided for Windows operating systems, Windows Server, Linux and MacOS, as non-limiting embodiments. Example Windows operating systems thatmay use the system may be Windows 10, Windows 8 and Windows 7. ExampleMac OS systems may be Lion (Mac OSA 10.7), Mountain Lion (Mac OS 10.8),Yosemite (Mac OS 10.10), El Capitan (Mac OS 10.11), Sierra and Mavericksas non-limiting embodiments. Supported browsers for the storage systemmay be, in non-limiting embodiments, Internet Explorer, Safari, Firefoxand Google Chrome.

Software may also be included in the system to allow for quick andautomatic backups of data according to user prescribed requirements.Such backup ability may be compliant with Windows based backup andrestore functions and/or Apple Time Machine requirements. Furthermore,software may be provided to add more than one user to the storagesystem. Users can be added or deleted according to an administrationaccount. Such administration account may also allow for restrictedaccess for certain users according to administration requirements.

Aspects of the disclosure relate to NVMe systems and processing ofcommands that are received, for example, from a host. In NVMe systems,processing of commands generally follows a sequence of phases. In afirst phase, the host device (a computer, cell phone or other computingdevice) places a command in a submission queue (SQ), and thereafternotifies the memory device that the command has been placed in asubmission queue. The NVME system reacts to the notification by the hostdevice, and the NVMe fetches the command from the submission queue.Thereafter, the NVMe processes the command according to the needs of thehost. In one non-limiting embodiment, the memory device performsinternal command selection, and then executes the command. The commandmay be a performance of a read or write command. After processing thecommand, the memory device places an entry on the completion queue, withthe entry indicating that the execution of the command has completed.The memory device then generates an interrupt command to the host deviceindicating that an entry has been placed on the completion queue. Afterthe placement of the command on the completion queue, the host devicereviews the data on the completion queue. The host device then notifiesthe memory device that the entry on the completion queue has beenreviewed.

A host device may use and configure multiple submission queues to aid inprocessing. The host device may place commands on respective submissionqueues which are then handled by the storage device and controller ofthe storage device. To enable the storage device to choose which commandon a submission queue to process, the memory device may use one or morearbitration schemes in order to determine the order of the commands tofetch from the multiple submission queues. One type of submission queueis an administrative submission queue, which includes administrativecommands to the memory device. Other queues may be submission queues.

In certain embodiments, the administrative submission queue may beassigned a high priority (or the highest priority relative to othersubmission queues). The other submission queues, however, may bepriorities that are lower than the administrative submission queue.Priority of the commands may proceed in the following order (indecreasing order of priority): urgent, high priority, medium priorityand low priority. Commands on other submission queues may relate to datatransfer, such as read commands (e.g. reading data from the flashmemory) and write commands (e.g., writing data to the flash memory). Thehost device may assign a respective priority to a submission queue atinitialization of the submission queue.

In determining which commands to fetch from the submission queues, analgorithm may be used. In one example embodiment, the memory device mayuse an arbitration algorithm, such as a round-robin algorithm or aweighted round-robin algorithm. These algorithms may determine the orderin which to fetch commands from multiple submission queues as well asadministrative queues. Using the round-robin algorithm, for example, thememory device selects the commands placed in the different submissionqueues in a symmetrical manner. The round-robin algorithm fetchescommands from the different queues in a predetermined order regardlessof priority of the submission queue. With the weighted round robinapproach, however, the memory device selects the commands placed in thedifferent submission queues in a non-symmetric way in which eachsubmission queue has its own priority assigned by the host device at theinitialization phase.

In one non-limiting embodiment, a weighted round robin algorithm maydetermine if there is a command that is urgent. The command may beplaced in the administrative submission queue or a submission queue. Ifthere is no command that is noted as urgent, then the weightedround-robin algorithm may weight commands on “high priority”, “mediumpriority”, and “low priority” submission queues to determine whichcommands to fetch (e.g. weight the commands on the high priority”submission queues higher than the commands on the “medium priority” or“low priority” submission queues.

In another non-limiting embodiment, the memory device may use a staticarbitration algorithm, such as a round robin approach, in which certainqueues are given higher priority than other queues. For example,fetching commands from an administrative submission queue may be givenhigher priority than fetching commands from other submission queues notdesignated as an administration queue since the administrative queue isassigned the highest priority.

In one implementation, the memory device may determine a priority forperforming the phases after fetching the command(s) from the queues. Asprovided above, example phases after fetching include: processing thecommand (e.g., performing internal command selection, executing thecommand, such as data transfer), posting the completion message; andgenerating an interrupt to the host device indicating that an entry hasbeen placed on the completion queue. The listed phases after fetchingare merely for illustrative purposes.

The memory device, such as an SSD, may determine priority for a command(or for performing one or more phases) based on one or more criteriaincluding any one, any combination or all of the following: (1) priorityof the respective command; (2) internals of the memory device (e.g., thestate of the die or the processing capability of the memory device, asdiscussed below); (3) power consumption; (4) state of the communicationinterface between the host device and the memory device (e.g., thestatus of the ingress and/or egress path); and (5) the phases of thecommands subject to execution. As a result, commands may be executedbased on a basis other than the time that a command was received.Different priorities may be placed on the above-identified criteria. Forexample, if the SSD is located within a laptop computer where batteryenergy is rapidly diminishing, power consumption parameters may be themost important priority factors. Thus, a delaying of the commands thatuse excessive power may be appropriate for a user.

The memory device may determine the priority of the command according toseveral methods. In a first method, a command priority may be determinedbased on the respective submission queue on which the command wasplaced. In differing implementations, upon initialization of aparticular submission queue, the host device may assign a priority tothe particular submission queue. Thereafter, the memory device maydetermine the particular submission queue on which the command wasplaced, and assign the priority of the particular submission queue tothe respective command. A host device may configure an administrativesubmission queue upon initialization and assign the highest priority, asdiscussed above, as such administrative submission queue activities maybe needed to be performed prior to conducting other less criticalactivities. In other specific implementations, the memory device maydetermine the priority for a respective completion queue based on thepriority of the submission queue that is associated with the respectivecompletion queue.

The memory device is configured to determine a priority of the commandsgiven to it based on one or more aspects of the command. As a firstexample, the memory device may use a Logical Block Address to determinethe priority of the respective command. For example, the memory devicemay assign a specific priority to a command that includes an addresswithin a given range that is frequently accessed by the memory device,than to other commands outside of a specific address range. In thisexample, commands that require access to specific ranges are processedmore quickly. In a second example, a type of command may be used toprovide instruction to the memory device on the level of priority forthe command. For example, a forced unit access (FUA) command is acommand that instructs the memory device to store data to the flashmemory (as opposed to storing the data in cache). In specificembodiments, the memory device may treat an FUA command as urgent as thememory device cannot post an entry to the completion queue for thiscommand until the data is stored in the flash memory. The memory devicecontroller, for example, may include a table that correlates types ofcommands to levels of urgency. In a third example, the memory device mayprioritize the command based on the size of the data transfer of thecommand. In particular, the memory device may prioritize commands thatdictate that small amount of data to be read from flash memory asopposed to comparatively larger amounts of data. In a fourth example,the memory device may analyze randomness of at least one aspectassociated with the command, and determine, based on the analyzedrandomness of at least one aspect associated with the command, anddetermine, based on the analyzed randomness, the priority of thecommand. In one example embodiment, a device, such as a memory deviceanalyzes the memory location (or set of locations) that are the subjectof a read command. In response to determining that the memorylocation(s) are random (no pattern of reading from this memorylocation), the memory device may assign a specific priority to thecommand. As an example, the specific priority may be a higher command.Thus, in one implementation, a higher degree of randomness of a commandmay indicate a greater importance to the host device compared tonon-random commands, and therefore correlates to a higher priorityassigned for the random command by the memory device. One phase after afetching operation is an internal command selection, which may comprise(1) command queuing and (2) command scheduling. In one implementation,the internal command selection may be performed by the memory devicebased on internals of the memory device, such as the internal statemachine of the memory device and/or the internal states of the flashdie(s). As an example, a die of the flash memory may be in one ofseveral states, and may unavailable for performing operations. Forexample, which data is being written to a flash die, the flash die is inthe program state and cannot be accessed. In another embodiment, if theflash die is performing garbage collection, the flash die may beunavailable. Execution of commands, such as read or write commands, isdependent on the state of the particular die. The memory devicecontroller may execute the commands on flash dies that are available foroperation. In a like manner, the memory device controller may delayexecution on flash dies that are unavailable. In another implementation,the memory device controller may select the phase of operation based onthe processing capacity of the memory device controller. As discussedherein, reads from the flash memory may further include errorcorrection, encryption or decryption, and the like. Operations of thesecommands and functions may be computationally intensive. As such,depending on the current processing capacity of the memory devicecontroller, the memory device controller may select phases of operation.For example, in response to determining that the memory devicecontroller's current processing capacity is reduced, the memory devicecontroller may select phases of operation that are less computationallyintensive (such as sending a read request to the host device). Inresponse to determining that the memory device controller has availableprocessing capacity, the memory device controller may select phases ofoperation that are more computationally intensive, the memory devicecontroller may select phases of operation that are more computationallyintensive (such as reading data from the flash memory, performing errorcorrection and decryption). In still another implementation, the memorydevice controller may arbitrate amongst commands that are in a samephase. Such arbitration may be accomplished through arbitrationarrangements placed within the controller. For example, a set ofcommands may be in the execution phase, such as performing a write to ora read from the flash memory. The memory device controller mayprioritize all commands that are operating in a particular phase (suchas the execution phase). Alternatively, the memory device controller mayprioritize a certain type of command that is operating in a particularphase (such as all read commands in the execution phase or all writecommands in the execution phase).

In another non-limiting embodiment, the memory device may perform aninternal command selection based on a priority associated with thecommand. As discussed above, priority may be determined in one ofseveral ways, including, for example, the priority of the submissionqueue from which the command was fetched, the type of command, or theaddress range of the command. In some implementations, the memory mayperform the internal command selection based on both the priorityassociated with the command and the internals of the memory device(e.g., the internal state machine of the memory device and/or theinternal states of the flash die(s)).

NVM Express is based on a paired submission and completion queuemechanism. Commands are placed by host software into a submission queuein the host and then transmitted to a solid state drive, for example.Completions (actions that are completed by the SSD) are placed into theassociated completion queue by the controller of the SSD. Submission andcompletion queues are allocated in host memory.

Enterprise SSD markets have different requirements, especially inquality of service (QoS) requirements. QoS is extremely important inenterprise operations and therefore strict requirements are defined.Several benchmarks have been established to test devices, such as SSDs,to ensure users have good results in specific areas. One example ofthese types of requirements is latency of input/output (I/O) commands.In SSDs, generally, there are strict requirements in performance, butnot in latency. In one example embodiment, requirements or benchmarksare established for random read commands. In this example embodiment, 99percent of the commands should be completed in 300 μS while 99.9% of thecommands should be completed in 400 μS. As provided in Table 1 below, amaximum timeout value is also provided. Furthermore, the number ofoperations needed in a specific test is provided in the right column.The center columns provide the number of μS needed under 4 kB, 8 kB and64 kB processing.

TABLE 1 Operations 4 kB 8 kB 64 kB Needed in (μs) (μs) (μs) Test*Average 240 250 450 —     99% (2 nines) 300 360 770 >100   99.9% (3nines) 400 380 1,000 >1,000   99.99% (4 nines) 500 550 3,000 >10,000 99.999% (5 nines) 1,000 2,000 3,500 >1e5  99.9999% (6 nines) 3,0004,000 5,000 >1e6 99.99999% (7 nines) 5,000 6,000 8,000 >1e7 99.999999% (8 nines) 7,000 8,000 10,000 >1e8 Maximum Timeout 11,000 12,000 20,000 —

According to Table 1, the percentages of completion are extremely highover a longer term test. Aspect herein provide for a storage device thatis highly optimized to achieve the requirements in Table 1, while notsignificantly impacting other criteria such as performance, power andarea. By logically processing needed commands, while delaying other,less necessary, commands, overall processing is improved for the user.Such processing methods are substantially different than conventionalprocesses that do not use informed or prioritized markers or flags oncommands signifying the need for urgent processing.

Aspects described herein do not add parallelism interconnections orlogical arrangements to achieve the requirements of Table 1. A devicecontroller that is adaptive and optimized for QoS in each step of theprocessing pipeline, from initiation to posting of an interrupt to ahost, is provided. For each command, the device controller captures atimestamp of a host issuing a relevant command “doorbell”. A first phaseof the pipeline involves a fetch command. An aging algorithm may also beadded to the NVMe queue arbitration algorithm so QoS requirements arenot lost. The next phase in the pipeline is command selection. At thisphase, the selection of the next command for execution is based on anintelligent QoS algorithm. All pending commands are evaluated andclassified into specific classes.

In a non-limiting embodiment, “Class A” commands may represent 99% ofthe commands (which must be completed in a range of between 300-400 μS).In a separate class, “Class B” commands account for a smaller percentageof commands, for example 0.9% (which must be completed within the300-400 μS timeframe). The above classifications may be based onevaluation and prediction and impacted by SLC/TLC zones, last accesstime and a doorbell timestamp. The command selection algorithm may takeall of these factors into account. An arbitration may be implemented ineach phase in the pipeline stages while each phase in the pipe has moreknowledge and therefore can adapt the arbitration by delaying orproviding higher priority to specific operations.

Referring to FIG. 1, an NVMe Round Robin arbiter is illustrated. Four(4) different command queues are illustrated providing an input into theRound Robin (RR) arbiter. One of the inputs comes from an administrativequeue (ASQ) and three of the inputs are provided from submission queues(SQ). As illustrated in FIG. 1, the Round Robin arbiter selects amongthe different command queues in a symmetric way.

Referring to FIG. 2, an NVMe Weighted Round Robin (WRR) arbiter isillustrated. The algorithm associated with this arbiter selects betweendifferent host SQs in a non-symmetrical manner wherein each queue hasits own priority assigned by a host at the initialization phase. Inorder to achieve results that are consistent with user expectations,commands are broken into urgent, high priority, medium priority, lowpriority and an ASQ section. ASQ's proceed under strict priority 1, thehighest priority possible. Urgent SQ are sorted through a RR arbiter andare designated as strict priority 2, or the next highest possiblepriority. High priority SQ's, medium priority SQ's and low priority SQ'sare processed through their own respective RR arbiter and then weightedas input into a WWR arbiter. The results from the WRR are designated asstrict priority 3. The WRR arbiter and the RR arbiters, described aselement3 330 below, in one embodiment, are part of the device controller324.

Non-volatile memory standards do not define arbitration algorithmsimplemented in a device controller, such as a SSD controller, forinternal operations. Aspects described herein disclose having QoS basedarbitrations in the device controller, as described later. These QoSbased arbitration based pipelines are optimized for providing superiorQoS operations, especially for enterprise operations. At each stage in apipeline, where a decision must be made on which operation should beperformed, an arbitration is performed, and the arbitration algorithmtakes into account the QoS requirements. All pending commands areevaluated and classified into specific classes. In one non-limitingembodiment, three (3) different types of classifications may be made.Class A, for example, represents 99% of the commands (which must becompleted in 300 μS), Class B represents 0.9% of the commands (whichmust be completed in the range of 300-400 μS), Class C represents 0.09%of the commands (which must be completed in the range of 400-500 μS).Other or different classifications may be made and the separation ofcommands into three different classes is merely illustrative. Forexample, if specific commands are known to affect performance more thanothers, but competing commands are noted as class B, then differingfactors may be used in ultimately scheduling the commands that areaffecting performance to a greater degree first. The arbitration logicselects the next command based on the classification and the remainingtime to achieve the goals of, for example, Table 1. The evaluation andcommand classification is based on the parameters discussed below.

Command Classification Parameters

-   -   1) Doorbell timestamp—this represents the time the device        controller gets a “doorbell” notification from the host        associated with this specific command.    -   2) SLC/TLC zone—this parameter represents where the relevant        user data is stored in the NAND is in SLC or TLC. SLC and TLC        zones have different parameters such as latency time and bit        error rate and are therefore considered in classification.    -   3) Die Utilization—die utilization may have an impact in the        classification. If the die is currently fully utilized, the next        command that uses this die will have a longer latency. Thus, if        commands are specifically destined for specific dies, rerouting        or delay of other less important commands may take place to        ensure speed of operation.    -   4) BER—(bit error rate) for the relevant physical address is        considered since the higher the BER is, the higher processing        time is needed for error correction.    -   5) Device Triggered Operations—some scheduled internal long        operations such as erase, garbage collection and relocations may        affect the classifications as well.        Current timestamp—this represents the current timestamp. This        value minus the doorbell stamp represents the time passed since        the host queued this command.

Based on the above parameters, the commands are classified. Based onthese classifications, the arbitration is done while taking into accountthe remaining time for each pending command. Once a command isclassified, the algorithm tries to complete the command in a maximumallowed value while providing other commands higher priority. Forexample, if a command is classified in Class C (i.e. must be completedin the range of 400-500 μS), the algorithm is optimized to complete thiscommand before the 500 μS passes, but not necessarily before 400 μS,thereby surpassing Class B commands. Such scheduling allows for othercommands to be completed. As one will understand, however, if no othercommands are scheduled to be completed prior to the 400 μS mark, theClass C commands may be executed immediately.

Referring to FIG. 3, a block diagram of a host computer system 300connected to a device 302 is illustrated. The host computer system 300provides an output which is classified as an ingress 304 to the device302. The host computer system 300 also accepts an egress 305 from thedevice 302. In the illustrated non-limiting embodiment, the device 302is a NAND based SSD. The host computer system 300 has a host memory thathas submission queues 308, completion queues 310, Physical Region Pages(PRP)s 312, data buffers 314, host memory buffers (HMB) 316 as well asother 318 memory components.

Further referring to FIG. 3, the device 302 is configured to store datawithin different memory arrays 320(1) through 320(10). Although shown ashaving ten (10) different arrays, more or less arrays may be provided.Data input and output from the memory arrays 320(1) through 320(10) isprovided through a data line 322. Such input and output passes to adevice controller 324.

The device controller 324 has several components to allow for processingof commands. Ingress 304 and egress 305 to the device 302 from the hostcomputer system 300 is performed through a PCIe MAC PHY interconnection326. If commands have been completed by the device controller 324 asspecified by a completion queue manager 328, then data may betransferred through the PCIe MAC PHY interconnection 326 to thecompletion queues 310 present in the host computer system 300.

Commands sent from the host computer system 300 that were originallyplaced in the submission queues 308 pass to the ingress 304, the PCIeMAC PHY interconnection 326, are time stamped by the doorbell timestamp336 and then continue to the command arbitration and fetcher 330. Thecommands are arbitrated according to a selected scheme, and then sent tocommand queueing 332 through the PCIe MAC PHY interconnection 326.Several queues may be used or filled when the command queueingarrangement 332 performs arbiter activities. A connected commandscheduler 334 may then schedule activities to be performed by the device302 based upon the command queuing. When commands are received from thesubmission queues 308 through the ingress 304 through the PCIe MAC PHYinterconnection 326, a doorbell time stamp may be attached by a doorbelltime stamp arrangement 336 to aid in the command arbitration 330 toensure that the performance of commands is proper in relation to Table1, as a non-limiting example.

After a command has been scheduled through the command scheduler 334, anaccess to memory units may be performed through a direct memory accessarrangement 338. In order to ensure that data is transferred effectivelyand not subject to latency, data transfers may be scheduled through adata transfer scheduler 340 that feeds information to the direct memoryaccess arrangement 338.

Error checking may be provided by the device controller 324 to ensurethat the data provided to the host computer 300 is free from errors. Anerror checking arrangement 342 may use different types of error checkingschemes in order to ensure that the data is correct. In one non-limitingembodiment, a parity check may be accomplished for the data. Other typesof embodiments are also possible. The error checking arrangement mayalso us a checksum routine. In still further embodiments, a cyclicredundancy check may be performed by the error correction arrangement342.

Interface between the device controller 324 and the memory arrays320(1)-320(10) is controlled through a flash interface module 344. Theflash interface module 344 is configured to interface with theindividual type of memory array provided. As will be understood, memoryarrays may be NAND based or NOR based, therefore the type of flashinterface module 344 is chosen according to the array used.

Referring to FIG. 4, a method 400 for performing a QoS based arbitrationfor a SSD is illustrated. At 402, a host sends a SQ doorbell to the SSD.At 404, the doorbell, which has been time stamped, is stored internallyof the SSD. At 406, a query is run to determine if a relevant commandwas fetched. If no relevant command was fetched, then the method loopsback to 406. At 408, if a relevant command was fetched at 406, then thedoorbell timestamp is attached to the command. At 410, more informationis collected from GAT. Such information may related to (SLC/TLC, biterror rate, etc.). At 412, the command completion time is estimated. At414, the command quality of service classification is provided. At 416,the command is performed according to the command QoS classification andscheduling operations.

In order to increase the performance of the solid state drive, thedevice may execute several commands in parallel. In non-limitingembodiments, the device may send several PRP fetching requests which areassociated with different NVMe commands. In the prior art, thearbitration mechanism was based only on the internal device states, suchas, for example, memory array status. Aspects of the disclosure hereininvolve taking into consideration the QoS requirements while evaluatingand classifying all pending commands and acting accordingly.

In NVMe, there may be several read requests generated by the host deviceto read data that is present within a memory array of the device. Theremay also be several write requests (as generated by the host device) towrite data to a memory array of the device. The memory device and thehost device may communicate using a transaction layer packet (TLP)request, as a non-limiting example. In one example (with the SQ residenton the host device), responsive to a TLP write request (sent via theingress path 104) by the host device 102 to the doorbell timestamp 136on the memory device (with the write to the doorbell register indicatingthat there is a command on the SQ), the memory device uses a TLP readrequest (sent via the egress path) to fetch the write command from theSQ (which is resident on the host device 100). The write command is arequest for the memory device to write data to the non-volatile memory.The memory device then parses the write command for information, such asan indication of a PRP pointer to a PRP list. For definitional purposes,the PRP list is a series of information, such as pointers or addresses,that indicate the location of the data in the host device. The memorydevice may then use another TLP read request to read data from thepointers or address in the PRP list. Thereafter, the memory deviceperforms the write command by storing data in non-volatile memory (e.g.flash memory) on the memory device. After storing the data in thenon-volatile memory, the memory device uses a TLP write request to writean entry to the completion queue (CQ) (indicating that the write commandhas been completed). The memory device may use a TLP write request togenerate an interrupt to the host device, with the interrupt signalingto the host device that there is an entry on the CQ. Responsive to theinterrupt, the host device reads the entry on the CQ and then issues aTLP write request to the CQ doorbell write register indicating that thehost device has reviewed the entry on the CQ. In the embodiment providedabove, the CQ and SQ may be resident in the device 102, such as in acontroller memory buffer.

In another example (again with the SQ and the CQ resident on the hostdevice), responsive to a TLP write request by the host to the doorbellregister on the memory device (with the write to the doorbell registerindicating that there is a command on the SQ), the memory device uses aTLP read request to fetch the read command from the SQ (which isresident on the host device). The read command is requested for thememory device to read data from the non-volatile memory and to send theread data to the host device. The memory device then reads thenon-volatile (e.g. flash memory) to read the data. The memory device canperform a series of operations on the data, such as error correction,encryption/decryption, etc., with storage buffers interspersed betweeneach of the serial operation. The read command may then be parsed forinformation, such as an indication of a PRP to a PRP list. The PRP listis a series of information, such as pointers or addresses, thatindicates the location in the host device to store the data that wasread from non-volatile memory (and optionally error corrected,encrypted, etc.). The memory device may use a TLP read request to readdata from the pointers or address in the PRP list. Afterward, a TLPwrite request is used to write the data that was read from non-volatilememory. After writing the data to the host device, the memory deviceuses a TLP write request to write an entry to the CQ (indicating theread command has been completed). The memory device then uses a TLPwrite request to generate an interrupt to the host device, with theinterrupt signaling to the host device that there is an entry on the CQ.Responsive to the interrupt, the host device reads the entry on the CQ,and then issues a TLP write request to a CQ doorbell write registerindicating that the host device has reviewed the entry on the CQ.

In the embodiments provided any suitable type of memory may be used.Semiconductor memory devices include volatile memory devices, such asdynamic random access memory (“DRAM”) or static random access memory(“SRAM”) devices, non-volatile memory devices, such as resistive randomaccess memory (“ReRAM”), electrically erasable programmable read onlymemory (“EEPROM”), flash memory (which can also be considered a subsetof EEPROM), ferroelectric random access memory (“FRAM”), andmagnetoresistive random access memory (“MRAM”) and other semiconductorelements capable of storing information may be used. Each type of memorydevice may have different configurations. For example, flash memorydevices may be configured in a NAND or a NOR configuration.

The memory devices can be formed from passive and/or active elements.Combinations may also be used. By way of a non-limiting example, passivesemiconductor memory elements include ReRAM device elements, which insome embodiments include a resistivity switching storage element, suchas an anti-fuse, phase change material, etc., and optionally a steeringelement, such as a diode, etc. Further by way of a non-limiting example,active semiconductor memory elements include elements containing acharge storage region, such as a floating gate, conductivenanoparticles, or a charge storage dielectric material.

Multiple memory elements may be configured so that they are connected inseries. In such configurations, each element may also be individuallyaccessible. By way of a non-limiting example, flash memory devices in aNAND configuration (NAND memory) may contain memory elements connectedin series. A NAND memory array may be configured so that the array iscomposed of multiple strings of memory in which a string is composed ofmultiple memory elements charging a single bit line and accessed as agroup. Alternatively, memory elements may be configured so that eachelement is individually accessible, e.g. a NOR memory array.

The semiconductor memory elements may be two or three dimensional typesof arrangements. The embodiments, therefore, are therefore not limitedto a specific arrangement for the memory elements.

In a two dimensional memory structure, the semiconductor memory elementsare arranged in a single plane or a single memory device level. In a twodimensional memory structure, for example, memory elements are arrangedin a plane (e.g. in an x-z direction plane) which extends substantiallyparallel to a major surface of a substrate that supports the memoryelements. As a non-limiting example, the substrate may include asemiconductor such as silicon.

The memory elements may be arranged in the single memory device level inan ordered array, such as in a plurality of rows and/or columns. Inother configurations, the memory elements may be arrayed in non-regularor non-orthogonal configurations. The memory elements may each have twoor more electrodes or contact lines, such as bit lines and word lines.

In embodiments where there is a three dimensional memory array, thethree dimensional memory array is arranged so that memory elementsoccupy multiple planes or multiple memory device levels, thereby forminga structure in three dimensions (i.e. in the x, y and z directions,where the y direction is substantially perpendicular and the x and zdirections are substantially parallel to the major surface of thesubstrate).

As a non-limiting example, a three dimensional memory structure may bevertically arranged as a stack of multiple two dimensional memory devicelevels. As another non-limiting example, a three dimensional memoryarray may be arranged as multiple vertical columns (e.g., columnsextending substantially perpendicular to the major surface of thesubstrate, i.e. in the y direction) with each column having multiplememory elements in each column. The columns may be arranged in a twodimensional configuration, e.g. in an x-z plane, resulting in a threedimensional arrangement of memory element with elements on multiplevertically stacked memory planes.

By way of non-limiting example, in a three dimensional NAND memoryarray, the memory element may be coupled together to form a NANDstrings. Other three dimensional configurations can be envisionedwherein some NAND strings contain memory elements in a single memorylevel while other strings contain memory elements which span throughmultiple memory levels. Three dimensional memory arrays may also bedesigned in a NOR configuration and in a ReRAM configuration.

In a monolithic three dimensional memory array, one or more memorydevice levels may be formed above a single substrate. Optionally, themonolithic three dimensional memory array may also have one or morememory layers at least partially within the single substrate. As anon-limiting example, the substrate may include different semiconductormaterials, such as silicon. In a monolithic three dimensional array, thelayers constituting each memory device level of the array are typicallyformed on the layers of the underlying memory device levels of thearray. Layers of adjacent memory device levels of a monolithic threedimensional memory array may be shared or have intervening layersbetween memory device levels.

Two dimensional arrays may be formed separately and then packagedtogether to form a non-monolithic memory device having multiple layersof memory. For example, non-monolithic stacked memories can beconstructed by forming memory levels on separate substrates and thenstacking the memory levels atop each other. The substrates may beremoved or reduced from the memory device levels before stacking, but asthe memory device levels are initially formed over separate substrates,the resulting memory arrays are not monolithic three dimensional memoryarrays. Further, multiple two dimensional memory arrays or threedimensional memory arrays may be formed on separate chips and thenpackaged together to form a stacked-chip memory device.

Circuitry may be required for operation of the memory elements and forcommunication with the memory elements. As a non-limiting example,memory devices may have circuitry used for controlling and drivingmemory elements to accomplish functions such as programming and reading.As another example, a controller for memory read-wire operations may belocated on a separate controller chip and/or on the same substrate asthe memory element.

In one non-limiting embodiment a method of operating a solid state driveis disclosed comprising receiving at least two commands from a hostrequiring an action by the solid state drive in a preliminary order,ordering the at least two commands based upon a quality of serviceclassification for the at least two commands to a final order andexecuting the at least two commands on the solid state drive in thefinal order, wherein an operational parameter of the solid state driveis modified by at least one of the at least two commands.

In another non-limiting embodiment, the method further comprises sendingthe at least two commands from the host to the solid state drive.

In another non-limiting embodiment, the method may further comprisesending a completion notification for each of the at least two commandsfrom the solid state drive to the host that each of the at least twocommands have been completed.

In another non-limiting embodiment, the method may further comprisesending an interrupt notification to the host upon sending thecompletion notification.

In another non-limiting embodiment, the method may further compriseattaching a time stamp indicating a time of arrival for each of the atleast two commands at the solid state drive.

In another non-limiting embodiment, the method may be performed whereinthe ordering of the at least two commands accounts for the time ofarrival for each of the commands.

In another non-limiting embodiment, the method may be performed whereinthe accounting for the time of arrival for each of the commands furthercomprises: estimating a time of completion for each of the at least twocommands based on the preliminary order of completion for each of the atleast two commands, comparing the estimated time of completion for eachof the at least two commands to a threshold, reordering the preliminaryorder of completion to the final order of completion if the estimatedtime of completion for each of the at least two commands exceeds thethreshold such that each of the at least two commands are completed bythe threshold in the final order of completion.

In another non-limiting embodiment, the method may be performed whereinthe reordering the preliminary order of completion accounts for a biterror rate.

In another non-limiting embodiment, the method may be performed whereinthe reordering the preliminary order of completion accounts for dieutilization.

In another non-limiting embodiment, the method may be performed whereinthe reordering the preliminary order of completion accounts for a typeof memory zone in which data is stored.

In another non-limiting embodiment, the method may be performed whereinthe reordering the preliminary order of completion involves a commandarbitration performed by a device controller.

In another non-limiting embodiment, the method may be performed whereinthe command arbitration is performed in a weighted round robinalgorithm.

In another non-limiting embodiment, the method may be performed whereinweights used for the weighted round robin algorithm are assigned to theat least two commands by the host.

In another non-limiting embodiment, the method may be performed whereinthe weights used are an administrative category, an urgent category, ahigh priority category, a medium priority category and a low prioritycategory.

In another non-limiting embodiment, a method of operating a memoryarrangement is disclosed comprising receiving at least two commands froma host through an interface of the memory arrangement, timestamping eachof the at least two commands upon receipt of the commands at theinterface, arbitrating each of the at least two commands to create afinal order for the performing each of the at least two commands andexecuting the at least two commands in the memory arrangement in thefinal order, wherein an operational parameter of the memory is modifiedby at least one of the at least two commands.

In another embodiment, the method may be accomplished wherein thearbitrating each of the at least two commands includes estimating a timeof execution of each of the at least two commands and comparing the timeof execution of each of the at least two commands to a threshold.

In another embodiment, the method may further comprise reordering thetime of execution of each of the at least two commands when thethreshold is exceeded.

In another embodiment, a device controller for a memory arrangementdevice is disclosed comprising an interface module configured totransmit and receive data from at least one memory array of the memoryarrangement device, a host interface module configured to transmit andreceive data from a host, a time stamp arrangement configured to recorda time when a command is received from the host through the hostinterface module, the time stamp arrangement connected to the hostinterface module, a command arbitration arrangement connected to thehost interface module, the command arbitration arrangement configured toreceive commands received by the host interface module and arbitrate anoperational order for the received commands; and a command queueingarrangement connected to the host interface and the interface module,wherein the command queueing arrangement is configured to acceptcommands placed in an order by the command arbitration arrangement.

In a further embodiment, the device controller may further comprise acompletion queue manager connected to the host interface module, whereinthe completion queue manager is configured to send a notification to thehost, through the host interface module of a completed command.

In a further embodiment, the device controller further comprises anerror correction arrangement connected to the interface module, whereinthe error correction arrangement is configured to identify and correcterrors in data received from the at least one memory array.

In another embodiment, a memory device is disclosed comprising at leastone memory array configured to store data provided to the array, aninterface module configured to transmit and receive data from at leastone memory array, a host interface module configured to transmit andreceive data from a host, a time stamp arrangement configured to recorda time when a command is received from the host through the hostinterface module, the time stamp arrangement connected to the hostinterface module, a command arbitration arrangement connected to thehost interface module, the command arbitration arrangement configured toreceive commands received by the host interface module and arbitrate anoperational order for the received commands; and a command queueingarrangement connected to the host interface and the interface module,wherein the command queueing arrangement is configured to acceptcommands placed in an order by the command arbitration arrangement.

In a further embodiment, the memory device is configured wherein the atleast one memory array is a non-volatile memory array.

In a further embodiment, the memory device is configured wherein thenon-volatile memory array is a NAND memory array.

In another embodiment, an arrangement for operating a solid state drive,is disclosed comprising: means for receiving at least two commands froma host requiring an action by the solid state drive in a preliminaryorder, means for ordering the at least two commands based upon a qualityof service classification for the at least two commands to a final orderand means for executing at least one command on the solid state drive ofthe at least two commands in the final order, wherein an operationalparameter of the solid state drive is modified by at least one of the atleast two commands.

In another embodiment, the arrangement may further comprise means forestimating a time of completion for each of the at least two commandsbased on the preliminary order of completion for each of the at leasttwo commands, means for comparing the estimated time of completion foreach of the at least two commands to a threshold and means forreordering the preliminary order of completion to the final order ofcompletion if the estimated time of completion for each of the at leasttwo commands exceeds the threshold such that each of the at least twocommands are completed by the threshold in the final order ofcompletion.

In a still further embodiment, the arrangement may further comprisemeans for sending the at least two commands from the host to the solidstate drive.

In a still further embodiment, the arrangement may further comprisemeans for sending a completion notification for each of the at least twocommands from the solid state drive to the host that each of the atleast two commands have been completed.

In another non-limiting embodiment, an apparatus for operating a memoryarrangement is disclosed comprising: means for receiving at least twocommands from a host through an interface of the memory arrangement,means for timestamping each of the at least two commands upon receipt ofthe commands at the interface, means for arbitrating each of the atleast two commands to create a final order for the performing each ofthe at least two commands, wherein the means for arbitrating isperformed through a weighted round robin algorithm and means forexecuting the at least two commands in the memory arrangement in thefinal order, wherein an operational parameter of the memory is modifiedby at least one of the at least two commands.

Need a “sum it all up with benefits” paragraph

In another non-limiting embodiment, an apparatus for operating a memoryarrangement is disclosed comprising: means for receiving at least twocommands from a host through an interface of the memory arrangement,means for timestamping each of the at least two commands upon receipt ofthe commands at the interface, means for arbitrating each of the atleast two commands to create a final order for the performing each ofthe at least two commands, wherein the means for arbitrating isperformed through a weighted round robin algorithm and means forexecuting the at least two commands in the memory arrangement in thefinal order, wherein an operational parameter of the memory is modifiedby at least one of the at least two commands.

What is claimed is:
 1. A method of operating a solid state drive,comprising: receiving at least two commands from a host requiring anaction by the solid state drive in a preliminary order; ordering the atleast two commands based upon a quality of service classification forthe at least two commands to a final order, wherein the ordering the atleast two commands comprises: estimating a time of completion for eachof the at least two commands based on the preliminary order ofcompletion for each of the at least two commands and a time stampindicating a time of arrival for each of the at least two commands atthe solid state drive; comparing the estimated time of completion foreach of the at least two commands to a threshold; and reordering thepreliminary order of completion to the final order of completion if theestimated time of completion for each of the at least two commandsexceeds the threshold such that each of the at least two commands arecompleted by the threshold in the final order of completion; andexecuting the at least two commands on the solid state drive in thefinal order, wherein an operational parameter of the solid state driveis modified by at least one of the at least two commands.
 2. The methodaccording to claim 1, further comprising: transmitting the at least twocommands from the host to the solid state drive.
 3. The method accordingto claim 1, further comprising: transmitting a completion notificationfor each of the at least two commands from the solid state drive to thehost that each of the at least two commands have been completed.
 4. Themethod according to claim 3, further comprising: sending an interruptnotification to the host from the solid state drive upon sending thecompletion notification.
 5. The method according to claim 1, furthercomprising: attaching the time stamp indicating the time of arrival foreach of the at least two commands at the solid state drive prior toordering the at least two commands.
 6. The method according to claim 1,wherein the ordering of the at least two commands accounts for the timeof arrival for each of the commands.
 7. The method according to claim 1,wherein the reordering the preliminary order of completion accounts fora bit error rate.
 8. The method according to claim 1, wherein thereordering the preliminary order of completion accounts for dieutilization.
 9. The method according to claim 1, wherein the reorderingthe preliminary order of completion accounts for a type of memory zonein which data is stored.
 10. The method according to claim 1, whereinthe reordering the preliminary order of completion involves a commandarbitration performed by a controller of the solid state drive.
 11. Themethod according to claim 10, wherein the command arbitration isperformed in a weighted round robin algorithm.
 12. The method accordingto claim 11, wherein weights used for the weighted round robin algorithmare assigned to the at least two commands by the host.
 13. The methodaccording to claim 12, wherein the weights used are an administrativecategory, an urgent category, a high priority category, a mediumpriority category and a low priority category.
 14. The method accordingto claim 1, wherein the ordering the at least two commands is based on aclassification of each of the two commands.
 15. The method according toclaim 14, wherein the command arbitration is performed in a weightedround robin algorithm, and wherein weights used for the weighted roundrobin algorithm are assigned to the at least two commands by the host,and wherein the weights used are an administrative category, an urgentcategory, a high priority category, a medium priority category and a lowpriority category.
 16. A method of operating a memory arrangement,comprising: receiving at least two commands from a host at the memoryarrangement through an interface of the memory arrangement in apreliminary order; timestamping each of the at least two commands uponreceipt of the commands at the interface; arbitrating each of the atleast two commands to create a final order for the performing each ofthe at least two commands, wherein the arbitrating each of the at leasttwo commands comprises: estimating a time of execution of each of the atleast two commands based on the preliminary order; comparing theestimated time of execution of each of the at least two commands to athreshold; and reordering the preliminary order of completion to thefinal order if the estimated time of execution for each of the at leasttwo commands exceeds the threshold such that each of the at least twocommands are completed by the threshold in the final order; andexecuting the at least two commands in the memory arrangement in thefinal order, wherein an operational parameter of the memory is modifiedby at least one of the at least two commands.
 17. The method accordingto claim 16, wherein the reordering the preliminary order of completioninvolves a command arbitration performed by a controller of the memoryarrangement.
 18. The method according to claim 16, further comprising:transmitting a completion notification for each of the at least twocommands from the memory arrangement to the host that each of the atleast two commands have been completed; and sending an interruptnotification to the host from the memory arrangement upon sending thecompletion notification.
 19. The method according to claim 16, whereinthe arbitrating each of the at least two commands is based on aclassification of each of the two commands.
 20. The method according toclaim 16, wherein the reordering the preliminary order of completionaccounts for a bit error rate and die utilization.
 21. An arrangementfor operating a solid state drive, comprising: means for receiving atleast two commands from a host requiring an action by the solid statedrive in a preliminary order; means for ordering the at least twocommands based upon a quality of service classification for the at leasttwo commands to a final order, wherein the means for ordering the atleast two commands comprises: means for estimating a time of completionfor each of the at least two commands based on the preliminary order ofcompletion for each of the at least two commands and an attached timestamp indicating a time of arrival for each of the at least two commandsat the solid state drive; means for comparing the estimated time ofcompletion for each of the at least two commands to a threshold; andmeans for reordering the preliminary order of completion to the finalorder of completion if the estimated time of completion for each of theat least two commands exceeds the threshold such that each of the atleast two commands are completed by the threshold in the final order ofcompletion; and means for executing at least one command on the solidstate drive of the at least two commands in the final order, wherein anoperational parameter of the solid state drive is modified by at leastone of the at least two commands.
 22. The arrangement according to claim21, further comprising: means for sending the at least two commands fromthe host to the solid state drive.
 23. The arrangement according toclaim 21, further comprising: means for sending a completionnotification for each of the at least two commands from the solid statedrive to the host that each of the at least two commands have beencompleted.
 24. The arrangement according to claim 21, wherein the meansfor reordering the preliminary order of completion accounts for a biterror rate.
 25. The arrangement according to claim 21, wherein the meansfor reordering the preliminary order of completion accounts for dieutilization.
 26. The arrangement according to claim 21, wherein themeans for reordering the preliminary order of completion accounts for atype of memory zone in which data is stored.
 27. The arrangementaccording to claim 21, further comprising: means for attaching the timestamps indicating the time of arrival for each of the at least twocommands at the solid state drive.
 28. An apparatus for operating amemory arrangement, comprising: means for receiving at least twocommands from a host through an interface of the memory arrangement in apreliminary order; means for timestamping each of the at least twocommands upon receipt of the commands at the interface; means forarbitrating each of the at least two commands to create a final orderfor the performing each of the at least two commands, wherein the meansfor arbitrating is performed through a weighted round robin algorithm,wherein the means for arbitrating each of the at least two commandscomprises: means for estimating a time of execution of each of the atleast two commands based on the preliminary order; means for comparingthe estimated time of execution of each of the at least two commands toa threshold; and means for reordering the preliminary order ofcompletion to the final order if the estimated time of execution foreach of the at least two commands exceeds the threshold such that eachof the at least two commands are completed by the threshold in the finalorder; and means for executing the at least two commands in the memoryarrangement in the final order, wherein an operational parameter of thememory is modified by at least one of the at least two commands.
 29. Theapparatus according to claim 28, further comprising: means fortransmitting a completion notification for each of the at least twocommands from the memory arrangement to the host that each of the atleast two commands have been completed; and means for sending aninterrupt notification to the host from the memory arrangement uponsending the completion notification.